Multireactive polymerizable mesogenic compounds

ABSTRACT

The invention relates to multireactive polymerizable mesogenic compounds of formula I
 
R 1 -MG-R 2   I
 
wherein R 1 , R 2  and MG have the meaning given in claim  1 , to a polymerizable mesogenic composition comprising at least two components, at least one which is a compound of formula I, to a linear or crosslinked polymer obtainable by polymerization of one or more compounds of formula I or of a polymerizable composition comprising one or more compounds of formula I and to the use of a compound of formula I, or a polymerizable composition or polymer obtainable thereof, in optical elements such as polarizers, optical retardation or compensation films, alignment layers, colour filters or holographic elements, in liquid crystal displays such as PDLC, polymer gel or polymer stabilized cholesteric texture (PSCT) displays, in adhesives, synthetic resins with anisotropic mechanical properties, cosmetics, diagnostics or liquid crystal pigments, for decorative and security applications, and for nonlinear optics or optical information storage.

This application is a divisional of U.S. Ser. No. 11/059,551, filed Feb.17, 2005 now U.S. Pat. No. 7,125,500, which is a divisional of U.S. Ser.No. 09/654,516, filed Sep. 1, 2000, now U.S. Pat. No. 7,060,200.

The invention relates to multireactive polymerizable mesogeniccompounds, to polymerizable liquid crystal compositions comprising themultireactive compounds, to linear or crosslinked liquid crystalpolymers obtainable from the multireactive compounds and thecompositions comprising them, and to the use of the multireactivepolymerizable mesogenic compounds, the polymerizable compositions andpolymers obtained therefrom in optical elements, liquid crystaldisplays, adhesives, synthetic resins with anisotropic mechanicalproperties, cosmetics, diagnostics, liquid crystal pigments, decorativeand security applications, nonlinear optics and optical informationstorage.

BACKGROUND OF THE INVENTION

Polymerizable mesogenic compounds, which are also known as reactivemesogenic compounds, have been described in prior art for variouspurposes. For example, they can be aligned in their liquid crystal phaseand subsequently polymerized in situ to give linear or crosslinkedliquid crystal polymer films with uniform orientation of high quality.These films can be used for example as optical elements, likepolarization filters as described in EP 0 397 263, broadband circularpolarizers as described in EP 0 606 940 and WO 97/35219, or compensationor retardation films as described in WO 98/00475, WO 98/04651 or WO98/12584.

For many applications it is preferred to use crosslinked polymer films,as these show higher stability and lower temperature dependence of theoptical properties, compared to films of linear polymers.

For this purpose, often polymerizable compositions are used whichtypically comprise a mixture of direactive and monoreactivepolymerizable mesogenic compounds.

The terms reactive or polymerizable mesogenic compound as used in theforegoing and the following comprise compounds with a rod-shaped,lath-shaped or disk-shaped mesogenic group, i.e. a group with theability to induce mesophase behaviour. These compounds do notnecessarily have to exhibit mesophase behaviour by themselves. It isalso possible that these compounds show mesophase behaviour only inmixtures with other compounds or when the polymerizable mesogeniccompounds or the mixtures comprising them are polymerized.

A di- or multireactive compound in this connection means a compoundhaving a mesogenic group and two or more polymerizable terminal groupsattached to one or both sides of the mesogenic group, either directly orvia a spacer group. A monoreactive compound means a compound having amesogenic group, to one side of which is attached a polymerizableterminal group, either directly or via a spacer, and to the other sideof which is attached a non-polymerizable terminal group, like e.g. apolar group such as halogen or cyano or a chiral or achiral alkyl oralkoxy group.

A typical example of a direactive polymerizable mesogenic compound ofthe prior art is compound (A)

wherein R is H or CH₃, which is described in EP 0 331 233 and in D. J.Broer et al., Makromol. Chem. 190, 2255-2268 (1989).

Typical examples of monoreactive polymerizable mesogenic compounds ofthe prior art are compounds (B) and (C)

wherein R is e.g. CN or OCH₃, which is described in DE 27 22 589,

which is described in DE 195,04,224.

SUMMARY OF THE INVENTION

When preparing polymerizable mesogenic compositions it is possible, byvarying the ratio of mono- and direactive compounds, to control thedegree of crosslinking of the resulting polymer film, and thereby totune its physical and chemical properties such as the glass transitiontemperature (in case of low or medium degree of crosslinking), thetemperature dependence of the optical properties, the thermal andmechanical stability, and the stability against organic solvents.

Furthermore, by varying the terminal group of the monoreactivepolymerizable mesogenic compound, it is possible to control the opticalproperties of the polymerizable mixture and the resulting film. Forexample, a helically twisted structure can be induced in the mixture andthe film by using compounds with a chiral terminal group. Furthermore,the inventors have found that it is possible in a polymerizablemesogenic mixture to control the orientation of the mesogenic compoundson a substrate or on a free surface by using compounds with polar andunpolar terminal groups in varying ratios.

In light of what was said above, it would be desirable to have availablepolymerizable mesogenic compounds that, when used in a polymerizablemixture, allow control, at the same time of the degree of crosslinkingand the optical properties of the resulting polymer film.

Furthermore, regarding the broad range of applications for polymerizablemesogenic compounds it is desirable for the expert to have availablefurther compounds of this type which are easy to synthesize and fulfillthe various requirements as described above.

The inventors have found that the above aims can be achieved byproviding multireactive polymerizable mesogenic compounds according tothe present invention.

The inventive compounds comprise two or more polymerizable groupsattached to the same side of a mesogenic core, whereas to the other sideof the mesogenic core there can be attached one or more polymerizablegroups or a non-polymerizable terminal group, like e.g. a polar orunpolar group or a chiral or achiral group.

Thus, when adding multireactive compounds according to the presentinvention to a polymerizable mixture, the degree of crosslinking of theresulting polymer film is increased. At the same time it is possible totailor the optical properties of the mixture and the polymer film byusing an inventive multireactive compound with an appropriately selectedterminal group at its free end.

The term ‘free end’ in this connection denotes the side of the mesogenicgroup of the inventive mesogenic compounds where no polymerizable groupis attached. Thus, when using inventive compounds in a polymerizablemixture it is possible inter alia

-   -   to control the alignment of the mixture on a substrate or on a        free surface by using inventive compounds with polar and unpolar        terminal groups at their free end in a specific ratio,    -   to induce a helically twisted liquid crystal phase, such as a        cholesteric or chiral phase, in the mixture by using an        inventive compound with a chiral terminal group at its free end,    -   to increase the birefringence of the mixture by using an        inventive compound with a highly birefringent terminal group at        its free end,    -   to increase the dielectric anisotropy of the mixture by using an        inventive compound with a polar terminal group at its free end,        while the two or more polymerizable groups at the opposite end        of the mesogenic core contribute to the crosslinking of the        polymer.

The inventive multireactive compounds wherein only one side of themesogenic group carries polymerizable groups, i.e. the other side is afree end, provide an additional benefit. In a polymerized film the freeend of an inventive multireactive polymerizable compound will not beconnected to the polymer backbone, in contrast e.g. to the direactiveprior art compound (A) above, wherein both ends of the mesogenic corewill be connected to the polymer backbone. As a consequence, the motionsof the mesogenic groups of inventive compounds are less restricted bythe polymer backbone during formation of the polymer network. This givesbetter alignment of the mesogenic groups and makes it easier to achieveuniform macroscopic orientation in a mixture comprising the inventivecompounds.

On the other hand, inventive compounds carrying two or morepolymerizable groups on each side of the mesogenic core are alsoadvantageous, as these compounds give more densely crosslinked polymernetworks with increased stability against heat, solvents and mechanicalstress, and wherein the uniform macroscopic orientation is more stable.Also, in case of these compounds a smaller amount is needed in apolymerizable mixture to obtain a densely crosslinked film, comparede.g. to direactive compounds of prior art, such as the above showncompound (A).

U.S. Pat. No. 5,750,213 discloses multireactive compounds of the formula

wherein m is 1, 6 or 12, n is 0, 6, 7, 11, 13 or 16 and v is 0 or 1.However, the compounds disclosed in U.S. Pat. No. 5,750,213 are notsubstituted in p-position of the biphenyl group. They do not show aliquid crystal phase and are liquid at room temperature. These areserious drawbacks for the use in polymerizable LC mixtures, sincecompounds without a liquid crystal phase lower the clearing point of aliquid crystal mixture, and liquid polymerizable compounds showincreased tendency towards spontaneous polymerization compared to solidcompounds, therefore they are less stable for storage, and increasedamounts of stabilizers are needed to prevent undesired polymerizationduring storage.

One object of the present invention is multireactive polymerizablemesogenic compounds of formula IR¹-MG-R²  Iwherein

-   R¹ is halogen, CN, OCN, NCS, NO₂ or a chiral or achiral alkyl    radical with 1 to 30 C atoms which may be unsubstituted, mono- or    polysubstituted by halogen or CN, it being also possible for one or    more non-adjacent CH₂ groups to be replaced, in each case    independently from one another, by —O—, —S—, —NH—, —N(CH₃)—, —CO—,    —COO—, —OCO—, —OCO—O—, —S—CO—, —CO—S—, —CH═CH— or —C≡C— in such a    manner that oxygen atoms are not linked directly to one another, or    alternatively R¹ has one of the meanings of R²or is denoting    P—(Sp-X)_(n)—,-   P is a polymerizable group,-   Sp is a spacer group with 1 to 25 C atoms,-   X is —O—, —S—, —CO—, —COO—, —OCO—, —OCO—O—, —CO—NH—, —NH—CO—,    —OCH₂—, —CH₂O—, —SCH₂—, —CH₂S—, —CH═CH—COO—, —OOC—CH═CH— or a single    bond,-   n is 0or 1,-   MG is a mesogenic group, and-   R² is straight-chain or branched alkyl with 1 to 25 C atoms which    may be unsubstituted, mono- or polysubstituted by halogen or CN, it    being also possible for one or more non-adjacent CH₂ groups to be    replaced, in each case independently from one another, by —O—, —S—,    —NH—, —N(CH₃)—, —CO—, —COO—, —OCO—, —OCO—O—, —S—CO—, —CO—S—, —CH═CH—    or —C≡C— in such a manner that oxygen atoms are not linked directly    to one another, and which is substituted with at least two-identical    or different groups P.

Another object of the invention is a polymerizable mesogenic compositioncomprising at least two components, at least one of which is a compoundof formula I.

Another object of the invention is a linear or crosslinked polymerobtainable by polymerization of one or more compounds of formula I or ofa polymerizable composition comprising one or more compounds of formulaI.

Yet another object of the invention is the use of a compound of formulaI, or a polymerizable composition or polymer obtainable therefrom, inoptical elements such as polarizers, optical retardation or compensationfilms, alignment layers, colour filters or holographic elements, inliquid crystal displays such as PDLC, polymer gel or polymer stabilizedcholesteric texture (PSCT) displays, in adhesives, synthetic resins withanisotropic mechanical properties, cosmetics, diagnostics or liquidcrystal pigments, for decorative and security applications, and fornonlinear optics or optical information storage. Upon further study ofthe specification and appended claims, further objects and advantages ofthis invention will become apparent to those skilled in the art.

Particularly preferred are compounds of formula I wherein R¹ is anon-polymerizable group.

Further preferred are compounds of formula I wherein R¹ has one of themeanings of R². Of these compounds, very preferred are those wherein R¹and R² have the same meaning.

Further preferred are compounds of formula I wherein MG is selected offormula II-(A¹-Z)_(m)-A²-  IIwherein

-   Z is in each case independently —O—, —S—, —CO—, —COO—, —OCO—,    —CO—NH—, —NH—CO—, —CH₂CH₂—, —OCH₂—, —CH₂O—, —SCH₂—, —CH₂S—, —CH═CH—,    —CH═CH—COO—, —OCO—CH═CH—, —C≡C— or a single bond,-   A¹ and A² are each independently 1,4-phenylene in which, in    addition, one or more CH groups may be replaced by N,    1,4-cyclohexylene in which, in addition, one or two non-adjacent CH₂    groups may be replaced by O and/or S, 1,4-cyclohexenylene,    1,4-bicyclo(2,2,2)octylene, piperidine-1,4-diyl,    naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, or    1,2,3,4-tetrahydro-naphthalene-2,6-diyl, it being possible for all    these groups to be unsubstituted, mono- or polysubstituted with F,    Cl, OH, CN, NO₂ or alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl    groups having 1 to 7 C atoms wherein one or more H atoms may be    substituted by F or Cl, and-   m is 1, 2 or 3.

Further preferred are compounds of formula I wherein P is selected fromCH₂═CW—COO—, WCH═CH—O—, CH₂═CH-Phenyl-(O)_(k)— and WHC—CH—, with W beingH, CH₃ or Cl and k being 0 or 1.

Further preferred are compounds of formula I wherein R² is substitutedwith 2, 3, 4 or 5 identical or different polymerizable groups P.

Particularly preferably R² is selected from the following subformulae—X-alkyl-CHP¹—CH₂—CH₂P²  Ia—X-alkyl-C(CH₂P¹)(CH₂P²)—CH₂P³  Ib—X-alkyl-CHP¹CHP²—CH₂P³  Ic—X-alkyl-C(CH₂P¹)(CH₂P²)—C_(a)H_(2a+1)  Id—X-alkyl-CHP¹—CH₂P²  Ie—X-alkyl-CHP¹P²  If—X-alkyl-CP¹P²—C_(a)H_(2a+1)  Ig—X-alkyl-C(CH₂P¹)(CH₂P²)—CH₂OCH₂—C(CH₂P³)(CH₂P⁴)CH₂P⁵  Ih—X-alkyl-CH((CH₂)_(a)P¹)((CH₂)_(b)P²)  Ii—X-alkyl-CHP¹CHP²—C_(a)H_(2a+1)  Ikwherein

-   alkyl is straight-chain or branched alkylene with 0 (i.e., a single    bond) to 12 C atoms which may be unsubstituted, mono- or    polysubstituted by halogen or CN, it being also possible for one or    more non-adjacent CH₂ groups to be replaced, in each case    independently from one another, by —O—, —S—, —NH—, —N(CH₃)—, —CO—,    —COO—, —OCO—, —OCO—O—, —S—CO—, —CO—S—, —CH═CH— or —C≡C— in such a    manner that oxygen atoms are not linked directly to one another,-   a and b are identical or different integers from 0 to 6,-   X has one of the meanings of formula 1, and-   P¹ to P⁵ have each independently one of the meanings of P given    above.

In the above preferred subformulae alkyl is especially preferably—(CH₂)_(c)—, with c being an integer from 0 to 12.

P and P¹ to P⁵ in formula I and the preferred subformulae are especiallypreferably, independently of each other, acrylate, methacrylate, vinyl,vinyloxy, epoxy or p-vinylphenyloxy.

A smaller group of preferred mesogenic groups of formula II is listedbelow. For reasons of simplicity, Phe in these groups is 1,4-phenylene,PheL is a 1,4-phenylene group which is substituted by 1 to 4 groups L,with L being F, Cl, CN, OH, NO₂ or an optionally fluorinated alkyl,alkoxy or alkanoyl group with 1 to 7 C atoms, and L Cyc is1,4-cyclohexylene. The following list of preferred mesogenic groupscomprises the subformulae II-1 to II-25 as well as their mirror images-Phe-Z-Phe-  II-1-Phe-Z-Cyc-  II-2-Cyc-Z-Cyc-  II-3-PheL-Z-Phe-  II-4-PheL-Z-Cyc-  II-5-PheL-Z-PheL-  II-6-Phe-Z-Phe-Z-Phe-  II-7-Phe-Z-Phe-Z-Cyc-  II-8-Phe-Z-Cyc-Z-Phe-  II-9-Cyc-Z-Phe-Z-Cyc-  II-10-Phe-Z-Cyc-Z-Cyc-  II-11-Cyc-Z-Cyc-Z-Cyc-  II-12-Phe-Z-Phe-Z-PheL-  II-13-Phe-Z-PheL-Z-Phe-  II-14-PheL-Z-Phe-Z-Phe-  II-15-PheL-Z-Phe-Z-PheL-  II-16-PheL-Z-PheL-Z-Phe-  II-17-PheL-Z-PheL-Z-PheL-  II-18-Phe-Z-PheL-Z-Cyc-  II-19-Phe-Z-Cyc-Z-PheL-  II-20-Cyc-Z-Phe-Z-PheL-  II-21-PheL-Z-Cyc-Z-PheL-  II-22-PheL-Z-PheL-Z-Cyc-  II-23-PheL-Z-Cyc-Z-Cyc-  II-24-Cyc-Z-PheL-Z-Cyc-  II-25

Particularly preferred are the subformulae II-1, II-2, II-4, II-6, II-7,II-8, II-11, II-13, II-14, II-15 and II-16.

In these preferred groups Z in each case independently has one of themeanings of Z¹ as given in formula I. Preferably Z is —COO—, —OCO—,—CH₂CH₂—, —C≡C— or a single bond.

Very preferably the mesogenic group MG is selected from the followingformulae and their mirror images

wherein L has the meaning given above and r is 0, 1 or 2.

The group

in these preferred formulae is very preferably denoting

furthermore

with L having each independently one of the meanings given above.

Particularly preferred are the subformulae IId, IIg, IIh, IIi, IIk andIIo, in particular the subformulae IId and IIk.

L is preferably F, Cl, CN, OH, NO₂, CH₃, C₂H₅, OCH₃, OC₂H₅, COCH₃,COC₂H₅, COOCH₃, COOC₂H₅, CF₃, OCF₃, OCHF₂, OC₂F₅, in particular F, Cl,CN, CH₃, C₂H₅, OCH₃, COCH₃ and OCF₃, most preferably F, Cl, CH₃, OCH₃and COCH₃.

In the compounds of formula I R¹ may be a polar or unpolar group.

In case R¹ is a polar group, it is preferably selected from CN, NO₂,halogen, OCH₃, OCN, NCS, COR³, COOR³ or a mono-, oligo- orpoly-fluorinated alkyl or alkoxy group with 1 to 4 C atoms. R³ isoptionally fluorinated alkyl with 1 to 4, preferably 1 to 3 C atoms.Halogen is preferably F or Cl. Especially preferably R¹ in thesecompounds is selected from F, Cl, CN, NO₂, OCH₃, COCH₃, COC₂H₅, COOCH₃,COOC₂H₅, CF₃, C₂F₅, OCF₃, OCHF₂, and OC₂F₅, in particular from F, Cl,CN, OCH₃ and OCF₃.

In case R¹ is an unpolar group, it is preferably alkyl with up to 15 Catoms or alkoxy with 2 to 15 C atoms.

If R¹ in formula I is an alkyl or alkoxy radical, i.e. where theterminal CH₂ group is replaced by —O—, this may be straight-chain orbranched. It is preferably straight-chain, has 2, 3, 4, 5, 6, 7 or 8carbon atoms and accordingly is preferably ethyl, propyl, butyl, pentyl,hexyl, heptyl, octyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy,or octoxy, furthermore methyl, nonyl, decyl, undecyl, dodecyl, tridecyl,tetradecyl, pentadecyl, methoxy, nonoxy, decoxy, undecoxy, dodecoxy,tridecoxy or tetradecoxy, for example.

Oxaalkyl, i.e. where one CH₂ group is replaced by —O—, is preferablystraight-chain 2-oxapropyl (=methoxymethyl), 2-(=ethoxymethyl) or3-oxabutyl (=2-methoxyethyl), 2-, 3-, or 4-oxapentyl, 2-, 3-, 4-, or5-oxahexyl, 2-, 3-, 4-, 5-, or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl or 2-, 3-, 4-, 5-,6-,7-, 8- or 9-oxadecyl, for example.

In the compounds of formula I R¹ may be an achiral or a chiral group. Incase of a chiral group it is preferably selected according to thefollowing formula III:

wherein

-   X¹ is —O—, —S—, —CO—, —COO—, —OCO—, —OCOO— or a single bond,-   Q¹ is an alkylene or alkylene-oxy group with 1 to 10 C atoms or a    single bond,-   Q² is an alkyl or alkoxy group with 1 to 10 C atoms which may be    unsubstituted, mono- or polysubstituted by halogen or CN, it being    also possible for one or more non-adjacent CH₂ groups to be    replaced, in each case independently from one another, by —C≡C—,    —O—, —S—, —NH—, —N(CH₃)—, —CO—, —COO—, —OCO—, —OCO—O—, —S—CO— or    —CO—S— in such a manner that oxygen atoms are not linked directly to    one another,-   Q³ is halogen, a cyano group or an alkyl or alkoxy group with 1 to 4    C atoms different from Q².

In case Q¹ in formula III is an alkylene-oxy group, the O atom ispreferably adjacent to the chiral C atom.

Preferred chiral groups R¹ are 2-butyl (=1-methylpropyl), 2-methylbutyl,2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2-propylpentyl, 2-octyl,in particular 2-methylbutyl, 2-methylbutoxy, 2-methylpentoxy,3-methylpentoxy, 2-ethylhexoxy, 1-methylhexoxy, 2-octyloxy,2-oxa-3-methylbutyl, 3-oxa-4-methylpentyl, 4-methylhexyl, 2-nonyl,2-decyl, 2-dodecyl, 6-methoxyoctoxy, 6-methyloctoxy,6-methyloctanoyloxy, 5-methylheptyloxycarbonyl, 2-methylbutyryloxy,3-methylvaleroyloxy, 4-methylhexanoyloxy, 2-chlorpropionyloxy,2-chloro-3-methylbutyryloxy, 2-chloro-4-methylvaleryloxy,2-chloro-3-methylvaleryloxy, 2-methyl-3-oxapentyl, 2-methyl-3-oxahexyl,1-methoxypropyl-2-oxy, 1-ethoxypropyl-2-oxy, 1-propoxypropyl-2-oxy,1-butoxypropyl-2-oxy, 2-fluorooctyloxy, 2-fluorodecyloxy for example.

In addition, compounds of formula I containing an achiral branched groupR¹ may occasionally be of importance, for example, due to a reduction inthe tendency towards crystallization. Branched groups of this typegenerally do not contain more than one chain branch. Preferred achiralbranched groups are isopropyl, isobutyl (=methylpropyl), isopentyl(=3-methylbutyl), isopropoxy, 2-methylpropoxy and 3-methylbutoxy.

Very preferably R¹ in formula I is halogen, cyano or an optionallyfluorinated achiral or chiral alkyl or alkoxy group with 1 to 15 Catoms.

Another preferred embodiment of the present invention relates tocompounds of formula I wherein R¹ is denoting P-(Sp-X)_(n)—.

P and P¹ to P⁵ in formula I are preferably an acrylate group, amethacrylate group, a vinyl or vinyloxy group, an epoxy group, a styrenegroup or a propenyl ether group, in particular an acrylate,methacrylate, vinyl or epoxy group.

As for the spacer group Sp in formula I all groups can be used that areknown for this purpose to the skilled in the art. The spacer group Sp ispreferably a linear or branched alkylene group having 1 to 20 C atoms,in particular 1 to 12 C atoms, in which, in addition, one or morenon-adjacent CH₂ groups may be replaced by —O—, —S—, —NH—, —N(CH₃)—,—CO—, —O—CO—, —S—CO—, —O—COO—, —CO—S—, —CO—O—, —CH(halogen)-, —CH(CN)—,—CH═CH— or —C≡C—.

Typical spacer groups are for example —(CH₂)_(o)—,—(CH₂CH₂O)_(p)—CH₂CH₂—, —CH₂CH₂—S—CH₂CH₂— or —CH₂CH₂—NH—CH₂CH₂—, with obeing an integer from 2 to 12 and p being an integer from 1 to 3.

Preferred spacer groups are ethylene, propylene, butylene, pentylene,hexylene, heptylene, octylene, nonylene, decylene, undecylene,dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene,ethylene-thioethylene, ethylene-N-methyliminoethylene, 1-methylalkylene,ethenylene, propenylene and butenylene for example.

Especially preferred are inventive compounds of formula I wherein Sp isdenoting an alkyl or alkoxy group with 2 to 8 C atoms. Straight-chainalkyl or alkoxy groups are especially preferred.

In another preferred embodiment of the invention the chiral compounds offormula I comprise at least one spacer group Sp that is a chiral groupof the formula IV:

wherein

-   Q¹ and Q³ have the meanings given in formula III, and-   Q⁴ is an alkylene or alkylene-oxy group with 1 to 10 C atoms or a    single bond, being different from Q¹.

In the event that R is denoting P-Sp-X—, the two spacer groups Sp in thecompounds of formula I may be identical or different.

Of the preferred compounds described above particularly preferred arethose wherein n is 1.

In another preferred embodiment of the present invention R¹ is aterminal chiral group selected from the following groups

an ethylenglycol derivative

wherein R⁴ is an alkyl radical with 1 to 12 C atoms,a group based on citronellol,

a cholesteryl group, a terpenoid radical as disclosed e.g. in WO96/17901, preferably selected from menthyl, neomenthyl, campheyl,pineyl, terpineyl, isolongifolyl, fenchyl, carreyl, myrthenyl, nopyl,geraniyl, linaloyl, neryl, citronellyl and dihydrocitronellyl,particularly preferably menthyl, a group selected from menthonederivatives like

or a terminal chiral sugar derivative comprising a mono- or dicyclicradical with pyranose or furanose rings like, for example, a terminalgroup derived from the chiral sugars disclosed in WO 95/16007.

In another preferred embodiment of the present invention the mesogenicgroup MG has at least one center of chirality.

In these compounds MG is preferably selected of formula VI-(A¹-Z)_(d)-G-(Z-A²)_(e)-  VIwherein

-   A¹, A² and Z have the meaning given in formula II,-   d and e are independently of each other 0, 1 or 2,-   and G is a bivalent chiral group.-   G in these compounds is preferably a chiral bivalent radical derived    from sugars, binaphthyl derivatives, or optically active glycols,    especially ethane-1,2-diol substituted in 1- and or 2-position with    alkyl or aryl groups. In case of sugar groups, these are preferably    selected from mono- and dicyclic groups comprising pentose or hexose    rings.

Particularly preferred are the following groups G

wherein Phe has the meaning given above, R⁴ is F or optionallyfluorinated alkyl with 1 to 4 C atoms and Y¹, Y², Y³ and Y⁴ have one ofthe meanings of R¹ in formula I.

Preferably G is dianhydrohexitol like dianhydrosorbitol

dianhydromannitol

and dianhydroiditol

especially preferably dianhydrosorbitol,substituted ethane diol like

wherein R⁴ is F, CH₃ or CF₃,or optionally substituted binaphthyl

wherein Y¹, Y², Y³ and Y⁴ are H, F or optionally fluorinated alkyl with1 to 8 C atoms.

The inventive compounds of formula I can be synthesized according to orin analogy to methods which are known per se and which are described instandard works of organic chemistry such as, for example, Houben-Weyl,Methoden der organischen Chemie, Thieme-Verlag, Stuttgart. Some specificmethods of preparation can be taken from the examples.

Furthermore, compounds of formula I wherein R² is selected of thepreferred subformulae Ia to Ik can be prepared according to or inanalogy to the reaction schemes 1 to 14 given below, followed byattaching polymerizable groups to the terminal OH groups byesterification or etherification according to known methods.

wherein R is -(A¹-Z)_(m)-R¹, A¹, Z and m have the meanings of formulaII, R¹ is an unpolymerizable polar or unpolar group as defined above,and R′ is an alkyl group with 1 to 10 C atoms.

The polymerizable groups can be attached to the terminal OH groups asdescribed for example in reaction scheme 15, or in analogy thereto.

An exemplary method of preparing inventive compounds wherein MG isselected of formula II is given in reaction scheme 16 below.

wherein R¹ is an unpolymerizable polar or unpolar group as definedabove, Z and m have the meaning of formula II, A and B are eachindependently Phe, PheL or Cyc as defined above, and L has one of themeanings given above.

The invention also relates to a polymerizable liquid crystal compositioncomprising at least two polymerizable components, at least one of whichis a compound of formula I, and to linear or crosslinked polymersprepared from the inventive compounds and compositions.

Suitable polymerizable mesogenic compounds that can be used asco-components of the polymerizable liquid crystal composition, togetherwith the inventive compounds of formula I, are disclosed for example inWO 93/22397; EP 0,261,712; DE 195,04,224; WO 95/22586 and WO 97/00600.The compounds disclosed in these documents, however, are to be regardedmerely as examples that shall not limit the scope of this invention.

Typical examples representing such polymerizable mesogenic compounds areshown in the following list of compounds, which should, however, betaken only as illustrative and is in no way intended to restrict, butinstead to explain the present invention:

In the above formulae, P has one of the meanings of formula I and itspreferred meanings as mentioned above, x and y are each independently 1to 12, A and D are 1 ,4-phenylene or 1,4-cyclohexylene, v is 0 or 1, Z⁰is —COO—, —OCO—, —CH₂CH₂— or a single bond, Y is a polar group, R⁰ is anunpolar alkyl or alkoxy group, Ter is a terpenoid radical like e.g.menthyl, Chol is a cholesteryl group, and L¹ and L² are eachindependently H, F, Cl, CN or an optionally halogenated alkyl, alkoxy orcarbonyl or group with 1 to 7 C atoms.

In a preferred embodiment of the invention the polymerizable liquidcrystalline composition comprises at least one multireactive compound offormula I and at least one mono- or direactive polymerizable compound,i.e. a mesogenic compound having one or two polymerizable groups.Especially preferred are monoreactive compounds selected of formulae V4to V15 and direactive compounds selected of formulae V1, V2 and V3above.

It is also possible for the inventive polymerizable liquid crystallinecomposition to comprise one or more non-polymerizable chiral compounds,which may be mesogenic or non-mesogenic, in addition or alternatively tochiral polymerizable compounds. For example, commercially availabledopants, like e.g. S 811, R 1011 or CB 15 (from Merck KGaA, Germany) canbe used for this purpose.

Especially preferred are chiral non-polymerizable dopants with a highhelical twisting power (HTP) selected of formula VII

and/or formula VIII

including the (R,S), (S,R), (R,R) and (S,S) enantiomers not shown,wherein E and F are each independently 1,4-phenylene ortrans-1,4-cyclohexylene, v is 0 or 1, Z⁰ is —COO—, —OCO—, —CH₂CH₂— or asingle bond, and R is alkyl, alkoxy or alkanoyl with 1 to 12 C atoms.

The compounds of formula VII and their synthesis are described in WO98/00428. The compounds of formula VIII and their synthesis aredescribed in GB 2,328,207.

Polymerizable liquid crystalline compositions are preferred thatcomprise 1 to 6, preferably 1 to 3 compounds of formula I.

In a preferred embodiment of the present invention the polymerizableliquid crystalline composition comprises 1 to 80% by weight, preferably2 to 60%, in particular 5 to 50% by weight of one or more compounds offormula I.

Particularly preferred are polymerizable compositions comprising

-   a1) 5 to 80%, very preferably 10 to 50% by weight of up to five,    preferably one or two compounds of formula I,-   a2) 5 to 90%, very preferably 10 to 40% by weight of up to five,    preferably one, two or three monoreactive mesogenic compounds,-   b) 0 to 25%, very preferably 1 to 10% by weight of a direactive    polymerizable mesogenic compound,-   c) 0.5 to 10%, very preferably 1 to 7% by weight of a polymerization    initiator,-   d) 0 to 5%, very preferably 0.1 to 2% by weight of a surfactant.

The compounds of component a2) are preferably selected from the aboveformulae V4 to V15, in particular from formulae V4 to V10.

The compounds of component b) are preferably selected from the aboveformula V1 and V2.

The term polar group as used in the foregoing and the following means agroup selected from halogen, CN, NO₂, OH, OCH₃, OCN, SCN, an optionallyfluorinated carbonyl or carboxyl group with up to 4 C atoms or a mono-oligo- or polyfluorinated alkyl or alkoxy group with 1 to 4 C atoms.Especially preferred polar groups are those as defined for Y¹ in formulaI, including its preferred meanings.

The term unpolar group means an alkyl group with 1 or more, preferably 1to 12 C atoms or an alkoxy group with 2 or more, preferably 2 to 12 Catoms.

Liquid crystalline polymers can be obtained from the inventivepolymerizable compounds and compositions e.g. by solution polymerizationor by in-situ polymerization.

For example, solution polymerization can be carried out in a solventlike dichloromethane, tetrahydrofuran or toluene using AIBN as aninitiator and heating for 24 hours at 30 to 60° C.

The in-situ polymerization of polymerizable liquid crystalline compoundsand compositions is described in detail by D. J. Broer et al., Makromol.Chem. 190, 2255ff. and 3202ff. (1989).

The polymerizable liquid crystal compounds and compositions according tothis invention are preferably polymerized in situ as described in theforegoing and the following.

The inventive compounds and polymerizable liquid crystallinecompositions are particularly useful for the preparation of anisotropicpolymer films, such as nematic or cholesteric polymer films, withuniform molecular orientation.

Thus, another object of the invention is an anisotropic polymer filmwith an oriented liquid crystalline phase that is obtainable bypolymerizing a polymerizable liquid crystalline composition comprisingat least one compound of formula I.

To prepare an anisotropic polymer film with uniform orientation, aninventive polymerizable mesogenic composition is preferably coated ontoa substrate, aligned and polymerized in situ by exposing them to heat oractinic radiation. Alignment and curing are preferably carried out inthe liquid crystalline phase of the composition.

Actinic radiation means irradiation with light, like UV light, IR lightor visible light, irradiation with X-rays or gamma rays or irradiationwith high energy particles, such as ions or electrons. As a source foractinic radiation for example a single UV lamp or a set of UV lamps canbe used. Another possible source for actinic radiation is a laser, likee.g. a UV laser, an IR laser or a visible laser.

When polymerizing by means of UV light, for example a photoinitiator canbe used that decomposes under UV irradiation to produce free radicals orions that start the polymerization reaction.

It is also possible to use a cationic photoinitiator, when curingreactive mesogens with for example vinyl and epoxide reactive groups,that photocures with cations instead of free radicals.

As a photoinitiator for radical polymerization for example thecommercially available Irgacure 651, Irgacure 184, Darocure 1173 orDarocure 4205 (all from Ciba Geigy AG) can be used, whereas in case ofcationic photopolymerization the commercially available UVI 6974 (UnionCarbide) can be used.

Preferably the polymerizable liquid crystalline composition comprises0.01 to 10%, in particular 0.05 to 8%, very preferably 0.1 to 5% byweight of a photoinitiator, especially preferably a UV-photoinitiator.

In addition to the components mentioned above, the polymerizablecomposition may also comprise one or more other suitable components suchas e.g. catalysts, stabilizers, chain-transfer agents, co-reactingmonomers or surface-active compounds. In particular the addition ofstabilizers is preferred in order to prevent undesired spontaneouspolymerization of the polymerizable material e.g. during storage.

As stabilizers in principal all compounds can be used that are known tothe skilled in the art for this purpose. These compounds arecommercially available in a broad variety. Typical examples forstabilizers are 4-ethoxyphenol or butylated hydroxytoluene (BHT).

Other additives, like e.g. chain transfer agents, can also be added tothe polymerizable material in order to modify the physical properties ofthe inventive polymer film. When adding a chain transfer agent, such asmonoreactive thiol compounds like e.g. dodecane thiol or multireactivethiol compounds like e.g. trimethylpropane tri(3-mercaptopropionate), tothe polymerizable material, the length of the free polymer chains and/orthe length of the polymer chains between two crosslinks in the inventivepolymer film can be controlled. When the amount of the chain transferagent is increased, the polymer chain length in the obtained polymerfilm is decreasing.

It is also possible, in order to increase crosslinking of the polymers,to add up to 20% of a non-mesogenic compound with two or morepolymerizable functional groups to the polymerizable compositionalternatively or additionally to di- or multireactive mesogeniccompounds.

Typical examples for direactive non-mesogenic monomers arealkyldiacrylates or alkyldimethacrylates with alkyl groups of 1 to 20 Catoms. Typical examples for non mesogenic monomers with more than twopolymerizable groups are trimethylpropanetrimethacrylate orpentaerythritoltetraacrylate.

In a preferred embodiment of the invention the polymerization of thepolymerizable composition is carried out under an atmosphere of inertgas, preferably under a nitrogen atmosphere.

As a substrate for example a glass or quartz sheet as well as a plasticfilm or sheet can be used. It is also possible to put a second substrateon top of the coated mixture prior to, during and/or afterpolymerization. The substrates can be removed after polymerization ornot. When using two substrates in case of curing by actinic radiation,at least one substrate has to be transmissive for the actinic radiationused for the polymerization.

Isotropic or birefringent substrates can be used. In case the substrateis not removed from the polymerized film after polymerization,preferably isotropic substrates are used.

Preferably at least one substrate is a plastic substrate such as forexample a film of polyester such as polyethyleneterephthalate (PET), ofpolyvinylalcohol (PVA), polycarbonate (PC) or triacetylcellulose (TAC),especially preferably a PET film or a TAC film. As a birefringentsubstrate for example an uniaxially stretched plastic film can be used.For example PET films are commercially available from ICI Corp. underthe trade name Melinex.

In a preferred embodiment of the present invention, the inventivepolymerizable composition is coated as a thin layer on a substrate orbetween two substrates and is aligned in its liquid crystal phase togive a uniform orientation.

A uniform orientation can be achieved for example by shearing themixture, e.g. by means of a doctor blade. It is also possible to applyan alignment layer, for example a layer of rubbed polyimide or sputteredSiO_(x), on top of at least one of the substrates. In some cases, themixtures orient themselves spontaneously on the substrate, or goodalignment is achieved already by the act of coating the mixture.

In another preferred embodiment, a second substrate is put on top of thecoated material. In this case, the shearing caused by putting togetherthe two substrates is sufficient to give good alignment. It is alsopossible to apply electric or magnetic fields to align the coatedmixture.

The polymerizable composition according to the present invention mayalso comprise one or more surfactants to improve planar alignment.Suitable surfactants are described for example in J. Cognard, Mol.Cryst. Liq. Cryst. 78, Supplement 1, 1-77 (1981). Particularly preferredare non-ionic surfactants, such as the commercially availablefluorocarbon surfactants Fluorad 171 (from 3M Co.), or Zonyl FSN (fromDuPont). Preferably the polymerizable mixture comprises 0.01 to 5%, inparticular 0.1 to 3%, very preferably 0.2 to 2% by weight ofsurfactants.

In some cases it is of advantage to apply a second substrate not only toaid alignment of the polymerizable mixture but also to exclude oxygenthat may inhibit the polymerization. Alternatively the curing can becarried out under an atmosphere of inert gas. However, curing in air isalso possible using suitable photoinitiators and high lamp power. Whenusing a cationic photoinitiator oxygen exclusion most often is notneeded, but water should be excluded.

For the preparation of anisotropic polymer gels, e.g. for use inswitchable liquid crystal display devices, the polymerizable compoundsor compositions can be polymerized in situ as described above, however,in this case alignment of the polymerizable mixture is not necessarilyrequired, although it may be desired for specific applications.

The invention also relates to the use of inventive compounds,compositions and polymers such as polarizers, optical retardation orcompensation films, alignment layers, colour filters or holographicelements, in liquid crystal displays such as PDLC, polymer gel orpolymer stabilized cholesteric texture (PSCT) displays, in adhesives,synthetic resins with anisotropic mechanical properties, cosmetics,diagnostics or liquid crystal pigments, for decorative and securityapplications, and for nonlinear optics or optical information storage.Inventive compounds comprising a chiral group can also be used as chiraldopants.

The inventive compounds of formula I are particularly suitable for thepreparation of oriented liquid crystal polymer films that can be used aspolarization or compensation films in liquid crystal displays.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The following preferred specific embodiments are,therefore, to be construed as merely illustrative, and not limitative ofthe remainder of the disclosure in any way whatsoever.

In the foregoing and in the following examples, all temperatures are setforth uncorrected in degrees Celsius; and, unless otherwise indicated,all parts and percentages are by weight.

The entire disclosure of all applications, patents and publications,cited above and below, and of corresponding European application No. 99116 849.3, filed Sep. 3, 1999, are hereby incorporated by reference.

EXAMPLES

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The following examples are, therefore, to beconstrued as merely illustrative and not limitative of the remainder ofthe disclosure in any way whatsoever.

In the foregoing and in the following examples, unless otherwiseindicated, all temperatures are set forth uncorrected in degrees Celsiusand all parts and percentages are by weight.

The following abbreviations are used to illustrate the liquidcrystalline phase behaviour of the compounds: K=crystalline; N=nematic;S=smectic; Ch=cholesteric; I=isotropic. The numbers between the symbolsindicate the phase transition temperatures in ° C.

Example 1

Compound (1) was prepared as follows according to reaction schemes 6 and15.

1a)

4′-Octyl-biphenyl-4-carboxylic acid (10.0 g, 32 mmol), thionyl chloride(3.0 ml, 1.3 equiv.) and 2 drops of N-methyl pyrrolidone were stirredunder reflux in DCM (100 ml) for 2 hours. The solution was evaporated todryness on a rotary evaporator. The residual brown oil which solidifiedon standing was used without further purification in the next step.

1b)

Acid chloride 1a (10.5 g, 32 mmol) was added to a solution of solketal(4.0 ml, 32 mmol) and pyridine (3.1 ml, 1.2 equiv., 38.4 mmol) in DCM(100 ml). The solution was stirred under reflux overnight, cooled toroom temperature and evaporated to dryness on a rotary evaporator. Theproduct was purified by flash chromatography (4:1 petroleum ether:ethylacetate) to leave upon evaporation of the appropriate fractions a yellowoil which solidified on standing. Yield 10.0 g, 95%, melting point 48°C. ¹H NMR showed the expected signals.

1c)

Acetal 1b (10.0 g, 23.6 mmol) was stirred in a solution of aqueousethanol (150 ml) in the presence of 2 ml conc. sulphuric acid for 2hours. The solution was cooled, concentrated in vacuo, water was addeduntil a white solid precipitated. The solid was collected by vaccumfiltration (4.9 g, 54%). IR (nujol mull) showed a broad O—H stretch at3500-3200 cm⁻¹.

The compound has a smectic phase, with K 91 S_(A) 114 I.

1)

Diol 1c (4.8 g, 12.5 mmol), 3-chloropropionyl chloride (2.4 ml, 25 mmol)and triethylamine (10.5 ml, 75 mmol) were dissolved in DCM (50 ml) andstirred at 35° C. for 16 hours. The solution was cooled, washed withwater, dried (Na₂SO₄) evaporated to dryness. The residual oil waspurified by flash column chromatography to leave an oil whichcrystallized on standing. Yield 5.3 g, 88%. ¹H NMR gave the expectedsignals.

The preceding examples can be repeated with similar success bysubstituting the generically or specifically described reactants and/oroperating conditions of this invention for those used in the precedingexamples.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention and, withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

1. A multireactive polymerizable mesogenic compound of formula IR¹-MG-R²  I wherein: R¹ is halogen, CN, OCN, NCS, NO₂ or an alkylradical with 1 to 30 C atoms which may be unsubstituted, mono- orpolysubstituted by halogen or CN, optionally one or more non-adjacentCH₂ groups being replaced, in each case independently from one another,by —O—, —S—, —NH—, —N(CH₃)—, —CO—, —COO—, —OCO—, —OCO—O—, —S—CO—,—CO—S—, —CH═CH— or —C≡C— in such a manner that oxygen atoms are notlinked directly to one another, or alternatively has one of the meaningsof R² or is P-(Sp-X)_(n)—; P is a polymerizable group; Sp is a spacergroup with 1 to 25 C atoms; X is —O—, —S—, —CO—, —COO—, —OCO—, —OCO—O—,—CO—NH—, —NH—CO—, —OCH₂—, —CH₂O—, —SCH₂—, —CH₂S—, —CH═CH—COO—,—OOC—CH═CH— or a single bond; n is 0 or 1; MG is a mesogenic group offormula VI-(A¹-Z)_(d)-G-(Z-A²)_(e)-  VI wherein Z is —O—, —S—, —CO—, —COO—, —OCO—,—CO—NH—, —NH—CO—, —CH₂CH₂—, —OCH₂—, —CH₂O—, —SCH₂—, —CH₂S—, —CH═CH—,—CH═CH—COO—, —OCO—CH═CH—, —C≡C— or a single bond, A¹ and A² are eachindependently 1,4-phenylene in which, in addition, one or more CH groupsare optionally replaced by N; 1,4-cyclohexylene in which, in addition,one or two non-adjacent CH₂ groups are optionally replaced by O and/orS; 1,4-cyclohexenylene; 1,4-bicyclo(2,2,2)octylene; piperidine-1,4-diyl;naphthalene-2,6-diyl; decahydronaphthalene-2,6-diyl; or1,2,3,4-tetrahydro-naphthalene-2,6-diyl; all these groups optionallybeing unsubstituted, mono- or polysubstituted with F, Cl, OH, CN, NO₂ oralkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl groups having 1 to 7 Catoms wherein one or more H atoms may be substituted by F or Cl, and dand e are independently of each other 0, 1 or 2, and G is a bivalentchiral group; and R² is alkyl with 1 to 25 C atoms which may beunsubstituted, mono- or polysubstituted by halogen or CN, optionally oneor more non-adjacent CH₂ groups being replaced, in each caseindependently from one another, by —O—, —S—, —NH—, —N(CH₃)—, —CO—,—COO—, —OCO—, —OCO—O—, —S—CO—, —CO—S—, —CH═CH— or —C≡C— in such a mannerthat oxygen atoms are not linked directly to one another, and which issubstituted with at least two identical or different groups P.
 2. Thecompound of claim 1, wherein P is a polymerizable group selected fromCH₂═CW—COO—, WCH═CH—O—, CH₂═CH-Phenyl-(O)_(k)— and

with W being H, CH₃ or Cl and k being 0 or
 1. 3. The compound of claim1, wherein G is a chiral bivalent radical derived from a sugar, abinaphthyl compound or an optically active glycol.
 4. The compound ofclaim 1, wherein G is a dianhydrohexitol group.
 5. The compound of claim1, wherein G is an ethane-1,2-diol group substituted in 1- and/or2-position with an alkyl or aryl group or groups.
 6. The compound ofclaim 1, wherein G is an optionally substituted binaphthyl group.
 7. Thecompound of claim 1, wherein G is a group selected from the followinggroups:

wherein Phe is 1,4-phenylene, R⁴ is F or optionally fluorinated alkylwith 1 to 4 C atoms, and Y¹, Y², Y³ and Y⁴ are each independently ishalogen, CN, OCN, NCS, NO₂ or an alkyl radical with 1 to 30 C atomswhich may be unsubstituted, mono- or polysubstituted by halogen or CN,optionally one or more non-adjacent CH₂ groups being replaced, in eachcase independently from one another, by —O—, —S—, —NH—, —N(CH₃)—, —CO—,—COO—, —OCO—, —OCO—O—, —S—CO—, —CO—S—, —CH═CH— or —C≡C— in such a mannerthat oxygen atoms are not linked directly to one another.
 8. A compoundaccording to claim 1, wherein R¹ is not a polymerizable group.
 9. Acompound according to claim 1, wherein R¹ has one of the meanings of R².10. A compound according to claim 1, wherein R² is a group of one of thefollowing formulae:—X-alkyl-CHP¹—CH₂—CH₂P²  Ia—X-alkyl-C(CH₂P¹)(CH₂P²)—CH₂P³  Ib—X-alkyl-CHP¹CHP²—CH₂P³  Ic—X-alkyl-C(CH₂P¹)(CH₂P²)—C_(a)H_(2a+1)  Id—X-alkyl-CHP¹—CH₂P²  Ie—X-alkyl-CHP¹P²  If—X-alkyl-CP¹P²—C_(a)H_(2a+1)  Ig—X-alkyl-C(CH₂P¹)(CH₂P²)—CH₂OCH₂—C(CH₂P³)(CH₂P⁴)CH₂P⁵  Ih—X-alkyl-CH((CH₂)_(a)P¹)((CH₂)_(b)P²)  Ii—X-alkyl-CHP¹CHP²—C_(a)H_(2a+1)  Ik wherein alkyl is alkylene with 1 to12 C atoms which may be unsubstituted, mono- or polysubstituted byhalogen or CN, one or more non-adjacent CH₂ groups optionally beingreplaced, in each case independently from one another, by —O—, —S—,—NH—, —N(CH₃)—, —CO—, —COO—, —OCO—, —OCO—O—, —S—CO—, —CO—S—, —CH═CH— or—C≡C— in such a manner that oxygen atoms are not linked directly to oneanother, a and b are identical or different integers from 0 to 6, X hasone of the meanings given in formula I, and P¹ to P⁵ independently haveone of the meanings of P given in formula I.
 11. A compound according toclaim 1, wherein each P is independently of each other acrylate,methacrylate, vinyl, vinyloxy, epoxy or p-vinylphenyloxy.
 12. A compoundaccording to claim 1, wherein Sp is an alkylene group having 1 to 20 Catoms, in which one or more non-adjacent CH₂ groups are optionallyreplaced by —O—, —S—, —NH—, —N(CH₃)—, —CO—, —O—CO—, —S—CO—, —O—COO—,—CO—S—, —CO—, —CH(halogen), —CH(CN)—, —CH═CH— or —C≡C—.
 13. A compoundaccording to claim 1, wherein R¹ is a chiral alkyl radical with 1 to 30C atoms which may be unsubstituted, mono- or polysubstituted by halogenor CN, optionally one or more non-adjacent CH₂ groups being replaced, ineach case independently from one another, by —O—, —S—, —NH—, —N(CH₃)—,—CO—, —COO—, —OCO—, —OCO—, —S—CO—, —CO—S—, —CH═CH— or —C≡C— in such amanner that oxygen atoms are not linked directly to one another,provided that sufficient C atoms and substituents or replacements areprovided to provide a chiral group.
 14. A polymerizable mesogeniccomposition comprising at least two components, wherein at least onecomponent is a compound of formula I of claim
 1. 15. A linear orcrosslinked polymer obtained by polymerizing a polymerizable mesogeniccompound of formula I of claim
 1. 16. A linear or crosslinked polymerobtained by polymerizing a polymerizable mesogenic composition accordingto claim
 14. 17. A polarizer, optical retardation or compensation film,alignment layer, colour filter, holographic element, liquid crystaldisplay, PDLC, polymer gel, polymer stabilized cholesteric texture(PSCT) display, adhesive, synthetic resin with anisotropic mechanicalproperties, cosmetic, diagnostic, liquid crystal pigment for decorativeand/or security applications, or article for nonlinear optics or opticalinformation storage comprising a compound of the formula I of claim 1.18. A polarizer, optical retardation or compensation film, alignmentlayer, colour filter, holographic element, liquid crystal display, PDLC,polymer gel, polymer stabilized cholesteric texture (PSCT) display,adhesive, synthetic resin with anisotropic mechanical properties,cosmetic, diagnostic, liquid crystal pigment for decorative and/orsecurity applications, or article for nonlinear optics or opticalinformation storage comprising a composition according to claim
 14. 19.A polarizer, optical retardation or compensation film, alignment layer,colour filter, hologrphic element, liquid crystal display, PDLC, polymergel, polymer stabilized cholesteric texture (PSCT) display, adhesive,synthetic resin with anisotropic mechanical properties, cosmetic,diagnostic, liquid crystal pigment for decorative and/or securityapplications, or article for nonlinear optics or optical informationstorage comprising a polymer according to claim 15.